my opinion is obviously biased so you can take this with a grain of salt
i havent skied in the park with anything under 90mm in two years, and last yr i skied park all yr with a 112mm waist, it takes a minor ajustment but once you get used to it i can almost garenty you'll never go back to a skinny ski. i think the biggest down side to a fatter ski is the weight but with faction thats not a n issued cuz there some of the lightest skis on the market.
all in all it really comes down to personal preferance, but with a wider ski in the park you'll also get a better all mt preformace wich is  a nice bonus.